1. Field of the Invention
This invention relates generally to steerable catheters. More particularly, the invention relates to a steerable catheter with a movable steering system for deflecting the distal-end region of the catheter in a variety of different profiles.
2. Description of the Related Art
The heart beat in a healthy human is controlled by the sinoatrial node (xe2x80x9cS-A nodexe2x80x9d) located in the wall of the right atrium. The S-A node generates electrical signal potentials that are transmitted through pathways of conductive heart tissue in the atrium to the atrioventricular node (xe2x80x9cA-V nodexe2x80x9d) which in turn transmits the electrical signals throughout the ventricle by means of the His and Purkinje conductive tissues. Improper growth of, or damage to, the conductive tissue in the heart can interfere with the passage of regular electrical signals from the S-A and A-V nodes. Electrical signal irregularities resulting from such interference can disturb the normal rhythm of the heart and cause an abnormal rhythmic condition referred to as xe2x80x9ccardiac arrhythmia.xe2x80x9d
While there are different treatments for cardiac arrhythmia, including the application of anti-arrhythmia drugs, in many cases ablation of the damaged tissue can restore the correct operation of the heart. Such ablation can be performed by percutaneous ablation, a procedure in which a catheter is percutaneously introduced into the patient and directed through an artery to the atrium or ventricle of the heart to perform single or multiple diagnostic, therapeutic, and/or surgical procedures. In such case, an ablation procedure is used to destroy the tissue causing the arrhythmia in an attempt to remove the electrical signal irregularities or create a conductive tissue block to restore normal heart beat or at least an improved heart beat. Successful ablation of the conductive tissue at the arrhythmia initiation site usually terminates the arrhythmia or at least moderates the heart rhythm to acceptable levels. A widely accepted treatment for arrhythmia involves the application of RF energy to the conductive tissue.
In the case of atrial fibrillation (xe2x80x9cAFxe2x80x9d), a procedure published by Cox et al. and known as the xe2x80x9cMaze procedurexe2x80x9d involves continuous atrial incisions to prevent atrial reentry and to allow sinus impulses to activate the entire myocardium. While this procedure has been found to be successful, it involves an intensely invasive approach. It is more desirable to accomplish the same result as the Maze procedure by use of a less invasive approach, such as through the use of an appropriate EP catheter system.
One such EP catheter system, as disclosed in U.S. Pat. Nos. 6,059,778 and 6,096,036, includes a plurality of spaced apart band electrodes located at the distal end of the catheter and arranged in a linear array. The band electrodes are positioned proximal heart tissue. RF energy is applied through the electrodes to the heart tissue to produce a series of long linear lesions similar to those produced by the Maze procedure. The catheters currently used for this procedure are typically flexible at the distal end, and the profile at the distal end is adjustable. However, when using such catheters, it is often difficult to conform the distal end profile to some of the irregular topographies of the interior cavities of the heart. In other instances, it is difficult for a multi-electrode catheter that is designed to produce long linear lesions to access and ablate tissue in regions that require short linear lesions, such as the so-called isthmus region that runs from the tricuspid annulus to the eustachian ridge. Ablation of tissue in this region, and other regions non-conducive to the placement of multi-electrode, long, linear-lesion ablation catheters within them, is best accomplished by delivering RF energy to a tip electrode to produce localized spot lesions or tip-drag lesions.
Proposed methods of ablating irregular topography areas and regions, such as the isthmus region, use a rigid introducer sheath in combination with a tip-electrode ablation catheter. The introducer sheath is used to position the tip electrode in the proper location. Once positioned, the electrode is either held in place by the sheath to produce a spot lesion or is dragged along the surface of the tissue, by the sheath, to produce a tip-drag lesion. The disadvantage of this system is that it requires the use of two instruments: the introducer sheath and the catheter. The use of an introducer sheath increases both instrument cost and patient trauma.
Other catheters for producing spot lesions or tip-drag lesions typically comprise a tip ablation electrode and a plurality of mapping band electrodes positioned at the distal end of the catheter. The catheters are steerable in that they are configured to allow the shape of the distal end of the catheter to be manipulated from a location outside the patient""s body. Steerable catheters that produce multiple bending profiles provide a broader range of steerability. However, known steerable catheters such as that disclosed in U.S. Pat. No. 5,195,968 have steering tendons attached to a ribbon, at or near the longitudinal centerline of the catheter. Because these tendons are fixed in place, the catheter is capable of providing only two types of steering profiles. As such, its ability to ablate within a biological site having cavities of various different shapes and sizes is limited.
Hence, those skilled in the art have identified a need for a catheter having a steerable distal-end region that is not limited to a select few deflection profiles but rather a variety of different profiles to improve access to difficult-to-reach locations of the human body. The present invention fulfills these needs and others.
Briefly, and in general terms, the present invention is directed to an electrophysiological (xe2x80x9cEPxe2x80x9d) catheter with a steerable, multi-profile distal-end region for maneuvering through and positioning within irregular topographic and difficult-to-reach locations of the human body.
In a first aspect, the invention relates to a catheter having a sheath with a proximal end, a distal-end region, and a lumen therebetween. The catheter also includes a steering system for deflecting the distal-end region and a positioning mechanism for adjusting the position of the steering system relative to the sheath. By providing a positioning mechanism that adjusts the position of the steering system, the present invention allows for the catheter flexible distal-end region to assume numerous different profiles to improve accessibility to difficult-to-reach locations of the human body.
In a detailed aspect of the invention, the steering system includes a core. The core is slidably disposed within the lumen and has a distal end positioned in the distal-end region of the sheath. The steering system also includes a lever located at the proximal end of the sheath and a tendon located within the lumen. The tendon has a first end attached to the core distal end and a second end attached to the lever. In a further detailed aspect, the core includes a distal tip and the first end of the tendon is attached thereto. In yet another detailed aspect, the core further includes a core base proximal the distal tip and a stylet extending between the core base and the core distal tip. In still another detailed facet, the core distal tip is fixed to the distal end of the stylet and the proximal end of the stylet is fixed to the distal end of the core base. In other detailed facets, the positioning mechanism may adjust the steering system to an advanced position to effect deflection at the distal end of the sheath distal-end region, or to a retracted position to effect deflection at the proximal-end region of the sheath distal-end region.
In another detailed facet, the positioning mechanism includes a handle having a proximal-end region and a distal-end region with the steering system core fixed thereto. The positioning mechanism also includes a cap that is fixed to the proximal end of the sheath. The cap is movable longitudinally along the distal-end region of the handle. In a further detailed facet, the cap includes a locking mechanism for locking the cap in place relative to the handle. In another further detailed facet, the distal-end region of the handle carries a plurality of recesses that interact with the locking mechanism.
In another detailed facet, the positioning mechanism includes a handle having the proximal end of the sheath fixed thereto. The positioning mechanism also includes a controller that is carried by the handle and attached to the core. The controller is movable longitudinally along the distal-end region of the handle. The positioning mechanism further includes a locking element that is carried by the handle and fixed to the core. The locking element is movable longitudinally along the distal-end region of the handle. The locking element is housed within the handle and is locked and released by a spring-loaded button that can engage in various locking positions. In yet another detailed facet, the distal-end region of the handle carries a plurality of positioning slots that interact with the locking element.
In a second aspect, the invention relates to a catheter having a sheath with a proximal end, a distal-end region and a lumen therebetween. The catheter also includes a core slidably disposed within the lumen with a distal end positioned in the distal-end region of the sheath. A tendon is located within the lumen and has a first end attached to the core distal end and a second end exiting the proximal end of the sheath. The catheter further includes a handle having the proximal end of the sheath fixed thereto, and a controller with a lever having the proximal end of the tendon attached and movable to effect axial displacement of the tendon. The controller, carried by the handle and attached to the core, is movable longitudinally along the distal-end region of the handle.
In a detailed aspect of the invention, longitudinal movement of the controller in the distal direction advances the core in the distal direction. In another detailed aspect, longitudinal movement of the controller in the proximal direction retracts the core in the proximal direction.
In a third aspect, the invention relates to a catheter having a sheath with a proximal end, a distal-end region, and a lumen therebetween. The catheter also includes a core. The core is slidably disposed within the lumen and has a proximal end and a distal end positioned in the distal-end region of the sheath. A tendon is located within the lumen and has a first end attached to the core distal end and a second end exiting the proximal end of the sheath. The catheter further includes a handle with a lever having the proximal end of the tendon attached and movable to effect axial displacement of the tendon. The handle has a proximal-end region and a distal-end region and the core fixed thereto. An adjustable cap is fixed to the proximal end of the sheath with the cap movable longitudinally along the distal-end region of the handle.
In a detailed aspect of the invention, longitudinal movement of the cap in the distal direction advances the sheath in the distal direction. In another detailed aspect, longitudinal movement of the cap in the proximal direction retracts the sheath in the proximal direction.
In yet another detailed aspect, the cap includes a locking mechanism for locking the cap in place relative to the handle. In another detailed aspect, the distal-end region of the handle carries a plurality of recesses that interact with the locking mechanism.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention.